Introduced in v8.2.0-rc0~74^2~2, QEMU now allows setting
.dynamic-memslots attribute for virtio-mem-pci devices. When
turned on, it allows memory exposed to guest to be split into
multiple memslots and thus smaller memory footprint (see the
original commit for detailed explanation).
Therefore, introduce new <target/> attribute which will control
that QEMU knob.
Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
docs/formatdomain.rst | 6 ++++++
src/conf/domain_conf.c | 18 +++++++++++++++++-
src/conf/domain_conf.h | 1 +
src/conf/schemas/domaincommon.rng | 5 +++++
.../memory-hotplug-virtio-mem.xml | 2 +-
5 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 96e03a3807..57974de9f4 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -8395,6 +8395,12 @@ Example: usage of the memory devices
The ``node`` subelement configures the guest NUMA node to attach the memory
to. The element shall be used only if the guest has NUMA nodes configured.
+ For ``virtio-mem`` optional attribute ``dynamicMemslots`` can be specified
+ (accepted values "yes"/"no") which allows hypervisor to spread memory into
+ multiple memory slots (allocate them dynamically based on the amount of
+ memory exposed to the guest), resulting in smaller memory footprint.
+ :since:`Since 10.0.0 and QEMU 8.2.0`
+
The following optional elements may be used:
``label``
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 82672b30a0..c53e72210c 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -13499,6 +13499,10 @@ virDomainMemoryTargetDefParseXML(xmlNodePtr node,
&def->target.virtio_mem.requestedsize, false, false) < 0)
return -1;
+ if (virXMLPropTristateBool(node, "dynamicMemslots", VIR_XML_PROP_NONE,
+ &def->target.virtio_mem.dynamicMemslots) < 0)
+ return -1;
+
addrNode = virXPathNode("./address", ctxt);
addr = &def->target.virtio_mem.address;
break;
@@ -21174,6 +21178,12 @@ virDomainMemoryDefCheckABIStability(virDomainMemoryDef *src,
src->target.virtio_mem.address);
return false;
}
+
+ if (src->target.virtio_mem.dynamicMemslots != dst->target.virtio_mem.dynamicMemslots) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("Target memory device 'dynamicMemslots' property doesn't match source memory device"));
+ return false;
+ }
break;
case VIR_DOMAIN_MEMORY_MODEL_DIMM:
@@ -25375,6 +25385,7 @@ virDomainMemoryTargetDefFormat(virBuffer *buf,
unsigned int flags)
{
g_auto(virBuffer) childBuf = VIR_BUFFER_INIT_CHILD(buf);
+ g_auto(virBuffer) attrBuf = VIR_BUFFER_INITIALIZER;
virBufferAsprintf(&childBuf, "<size unit='KiB'>%llu</size>\n", def->size);
if (def->targetNode >= 0)
@@ -25414,6 +25425,11 @@ virDomainMemoryTargetDefFormat(virBuffer *buf,
if (def->target.virtio_mem.address)
virBufferAsprintf(&childBuf, "<address base='0x%llx'/>\n",
def->target.virtio_mem.address);
+
+ if (def->target.virtio_mem.dynamicMemslots) {
+ virBufferAsprintf(&attrBuf, " dynamicMemslots='%s'",
+ virTristateBoolTypeToString(def->target.virtio_mem.dynamicMemslots));
+ }
break;
case VIR_DOMAIN_MEMORY_MODEL_SGX_EPC:
@@ -25423,7 +25439,7 @@ virDomainMemoryTargetDefFormat(virBuffer *buf,
break;
}
- virXMLFormatElement(buf, "target", NULL, &childBuf);
+ virXMLFormatElement(buf, "target", &attrBuf, &childBuf);
}
static int
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 14901b37ba..6e45b7fb6e 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2674,6 +2674,7 @@ struct _virDomainMemoryDef {
unsigned long long currentsize; /* kibibytes, valid for an active
domain only and parsed */
unsigned long long address; /* address where memory is mapped */
+ virTristateBool dynamicMemslots;
} virtio_mem;
struct {
} sgx_epc;
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index f318c06797..08c408e138 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -7260,6 +7260,11 @@
<define name="memorydev-target">
<element name="target">
+ <optional>
+ <attribute name="dynamicMemslots">
+ <ref name="virYesNo"/>
+ </attribute>
+ </optional>
<interleave>
<element name="size">
<ref name="scaledInteger"/>
diff --git a/tests/qemuxml2argvdata/memory-hotplug-virtio-mem.xml b/tests/qemuxml2argvdata/memory-hotplug-virtio-mem.xml
index c578209d8a..359ece7a77 100644
--- a/tests/qemuxml2argvdata/memory-hotplug-virtio-mem.xml
+++ b/tests/qemuxml2argvdata/memory-hotplug-virtio-mem.xml
@@ -60,7 +60,7 @@
<nodemask>1-3</nodemask>
<pagesize unit='KiB'>2048</pagesize>
</source>
- <target>
+ <target dynamicMemslots='yes'>
<size unit='KiB'>2097152</size>
<node>0</node>
<block unit='KiB'>2048</block>
--
2.41.0
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